Currently, molding plastic materials, rubber materials, and other polymeric materials using molds requires the use of mold-releasing agents, such as silicone oil, wax, talc, mica, and tetrafluoroethylene resin. Although silicone oil, wax, etc., have excellent mold releasability, such mold-releasing agents are transferred to molded products, thereby impairing the uniform coating properties, secondary processability, etc., of the molded products; in addition, the durability of mold release effect is not sufficient. As for tetrafluoroethylene resin, the durability of mold release effect and secondary processability are satisfactory; however, it is necessary to perform bake treatment to form a film on the molding surface of a mold in the mold-release process, and the same treatment is required for reprocessing. Consequently, many processes are required.
In order to solve these defects, mold-releasing agents comprising a C4-C20 polyfluoroalkyl group-containing phosphate ester as one of their active ingredients are proposed (see Patent Documents 1 to 3). These mold-releasing agents exhibit excellent mold releasability and have a longer mold release life than conventional mold-releasing agents; however, as the shape of molded products becomes more complicated in recent years, the mold-releasing agents are required to achieve much higher performance.
Meanwhile, polyfluoroalkylphosphonic acid esters are also widely used as starting materials for the synthesis of active ingredients of mold-releasing agents. The mold release performance of polyfluoroalkylphosphonic acids, when used as mold-releasing agents, is most likely developed in compounds having a perfluoroalkyl group containing 8 to 12 carbon atoms. In particular, phosphonate compounds having a perfluorooctyl group and represented by the formula:CF3(CF2)7CH2CH2P(O)(OH)2 are preferably used in this kind of application (see Patent Documents 4 to 7).
Incidentally, it is reported that phosphate or phosphonate compounds having a C8-C12 perfluoroalkyl group are biologically degraded in the environment and converted to compounds having relatively high bioaccumulation potential and environmental concentration, causing concerns for exposure during treatment processes, and release and diffusion from waste, treated base materials, etc., into the environment. Moreover, compounds having a perfluoroalkyl group containing 14 or more carbon atoms are very difficult to handle because of their physical and chemical properties, and hence, such compounds are rarely used in practice.
Furthermore, as for phosphate or phosphonate compounds having a perfluoroalkyl group containing 8 or more carbon atoms, generation and incorporation of perfluorooctanoic acids with high bioaccumulation potential is unavoidable during the production of these compounds. For these reasons, companies that produce such phosphate or phosphonate compounds have retreated from the production of the compounds or promoted the use of alternative compounds having a perfluoroalkyl group containing 6 or less carbon atoms.
However, compounds having a perfluoroalkyl group containing 6 or less carbon atoms cause a significant decrease in orientation on the surface of a treated substrate, and the melting point, glass transition point (Tg), etc., of the compounds are markedly lower than those of C8 compounds. Accordingly, the compounds are highly influenced by their environmental conditions, such as temperature, humidity, stress, and contact with an organic solvent. Consequently, the desired performance cannot be sufficiently achieved, and durability and other properties are affected.